1. Field of the Invention
The present invention relates to a dynamic image processing method, a dynamic image processor, and a dynamic image display device.
2. Description of the Related Art
As recent development of computer games and progress of computer graphics technology have been on the increase, various images and TV are displayed on a computer display device. Such images may include dynamic images which exhibit a large and high speed variation in brightness over time, for example, glaring dynamic images with high speed motions and intensive flashes. Such dynamic images provide a stress to a viewer who looks the display screen. It has been confirmed that such images cause a video display terminal stress which may cause a light sensibility trouble of the viewer.
The brightness variation over time at a frequency band from about 7 Hz to 60 Hz including 10 Hz is particularly sensible to the human. Japanese laid-open patent publication No. 2795214 discloses that to countermeasure the above problem, a time-filter is used to the dynamic image signal with the above brightness variation. The influence by the variation in brightness over time is reduced as follows. The variation in brightness signals or RGB-signals over time are processed by the time filter to attenuate a frequency component in the above influential frequency band for reducing the excessive stress to the viewer. Each of the RGB-signals may optionally be converted from analog signals to digital signals, so that the brightness of the digital signals or respective signal values are then processed by the time-filter. The most sensible frequency to the human may be confirmed by displaying white-and-black flashes over a gray-background with variations in contrast between white and black and in frequency.
The variation in brightness over time of the entirety of the image is extracted, so that only if the extracted variation exceeds a predetermined value, then the time filter processing is executed. The image may be represented by the analog or digital signals. The magnitude of variation in brightness over time or the magnitude of variation in RGB-signal values is integrated over an entirety of the display screen, so that a magnitude of the attenuation is adjusted in accordance with the integrated magnitude value.
A difference in brightness between a moving object of the dynamic image and the background image is detected. Namely, all of the moving objects are uniformly subjected to the time-filter independent from a displacement of the object with reference to a visual field and a relative speed to the visual field.
The recognition of the object moving over the dynamic image may be made by either an inter-frame differential coding method, a moving vector detecting method and a gradient method. Those methods may be optionally selected in consideration of the word load level, the hardware conditions, the quality of image and costs.
The above-described conventional technique is to subject moving objects to the uniform time-filtering process, whereby edges of the object on the image are non-sharp, and the motion of the object makes the viewer to feel not natural thereto.
In the above circumstances, the development of a novel dynamic image processing method, a dynamic image processor and a dynamic image display device free from the above problems is desirable.